Properties of emulsions stabilised by sodium caseinate–chitosan complexes

Oil-in-water emulsions (10%, w/w, oil) were prepared at pH 5.7 by using electrostatically formed complexes of 0.5% (w/w) sodium caseinate (Na-CAS) and 0–0.6% (w/w) chitosan. Emulsions stabilized by complexes with increased levels of chitosan (>0.2% w/w) had a smaller average droplet size and exhibited greater stability during storage. All chitosan containing emulsions exhibited a slight shear thinning behaviour with increased high-shear-rate viscosity at higher chitosan levels. Even though complexing of Na-CAS with chitosan resulted in a delay of the adsorption of the surface active components at the oil/water interface, the presence of chitosan did not significantly influence the rheological properties of the formed interfaces. Acid-induced aggregation was observed only for the emulsion that was stabilized solely by Na-CAS when the pH dropped close to the isoelectric point of the protein component, resulting in flocculation and large increase in the storage modulus.